Maternal cocaine administration in mice alters DNA methylation and gene expression in hippocampal neurons of neonatal and prepubertal offspring

Previous studies documented significant behavioral changes in the offspring of cocaine-exposed mothers. We now explore the hypothesis that maternal cocaine exposure could alter the fetal epigenetic machinery sufficiently to cause lasting neurochemical and functional changes in the offspring. Pregnant CD1 mice were administered either saline or 20 mg/kg cocaine twice daily on gestational days 8-19. Male pups from each of ten litters of the cocaine and control groups were analyzed at 3 (P3) or 30 (P30) days postnatum. Global DNA methylation, methylated DNA immunoprecipitation followed by CGI(2) microarray profiling and bisulfite sequencing, as well as quantitative real-time RT-PCR gene expression analysis, were evaluated in hippocampal pyramidal neurons excised by laser capture microdissection. Following maternal cocaine exposure, global DNA methylation was significantly decreased at P3 and increased at P30. Among the 492 CGIs whose methylation was significantly altered by cocaine at P3, 34% were hypermethylated while 66% were hypomethylated. Several of these CGIs contained promoter regions for genes implicated in crucial cellular functions. Endogenous expression of selected genes linked to the abnormally methylated CGIs was correspondingly decreased or increased by as much as 4-19-fold. By P30, some of the cocaine-associated effects at P3 endured, reversed to opposite directions, or disappeared. Further, additional sets of abnormally methylated targets emerged at P30 that were not observed at P3. Taken together, these observations indicate that maternal cocaine exposure during the second and third trimesters of gestation could produce potentially profound structural and functional modifications in the epigenomic programs of neonatal and prepubertal mice.     

人皮肤成纤维细胞中α1(Ⅰ)前胶原基因转录调控研究

为寻找纤维化形成中调控人Ⅰ型前胶原基因高水平转录的启动序列及其DNA结合蛋白 ,以人皮肤成纤维细胞α1(Ⅰ )前胶原基因转录起始点上游 - 2 5kb至 + 4 2bp的片段为靶序列 ,采用PCR、基因重组、报告基因测活、细胞基因转染技术比较不同长短启动子活性 .凝胶滞留实验 (EM SA)研究高启动活性片段相应的DNA结合蛋白 .基因转染高活性转录因子识别序列至靶细胞 ,探讨前胶原基因激活阻断的新手段 .结果表明 ,- 2 4 83～ + 4 2bp、 - 2 6 8～ + 4 2bp序列具有强启动调控活性 ,而 - 10 5～ + 4 2bp片段启动活性最低 .EMSA对高启动活性小片段DNA结合蛋白的分析提示 ,- 2 6 8～ + 4 2bp序列中存在转录因子Ap 1、Sp 1、NF 1的特异结合位点 .转染高活性转录因子识别序列Ap 1、Sp 1至靶细胞可竞争性阻断胶原基因启动转录激活 .研究提示 ,人α1(Ⅰ )前胶原基因 - 2 4 83～ + 4 2bp、 - 2 6 8～ + 4 2bp片段有高启动活性 .转录因子Ap 1、Sp 1、NF 1与 - 2 6 8～ + 4 2bp序列中相应识别序列的结合与其基础高转录活性有关 .转染高活性转录因子识别序列Ap 1、Sp 1可从转录水平阻断胶原基因的激活     

Kidney Dysfunction in Adult Offspring Exposed In Utero to Type 1 Diabetes Is Associated with Alterations in Genome-Wide DNA Methylation

Background

Fetal exposure to hyperglycemia impacts negatively kidney development and function.

Objective

Our objective was to determine whether fetal exposure to moderate hyperglycemia is associated with epigenetic alterations in DNA methylation in peripheral blood cells and whether those alterations are related to impaired kidney function in adult offspring.

Design

Twenty nine adult, non-diabetic offspring of mothers with type 1 diabetes (T1D) (case group) were matched with 28 offspring of T1D fathers (control group) for the study of their leukocyte genome-wide DNA methylation profile (27,578 CpG sites, Human Methylation 27 BeadChip, Illumina Infinium). In a subset of 19 cases and 18 controls, we assessed renal vascular development by measuring Glomerular Filtration Rate (GFR) and Effective Renal Plasma Flow (ERPF) at baseline and during vasodilatation produced by amino acid infusion.

Results

Globally, DNA was under-methylated in cases vs. controls. Among the 87 CpG sites differently methylated, 74 sites were less methylated and 13 sites more methylated in cases vs. controls. None of these CpG sites were located on a gene known to be directly involved in kidney development and/or function. However, the gene encoding DNA methyltransferase 1 (DNMT1)—a key enzyme involved in gene expression during early development–was under-methylated in cases. The average methylation of the 74 under-methylated sites differently correlated with GFR in cases and controls.

Conclusion

Alterations in methylation profile imprinted by the hyperglycemic milieu of T1D mothers during fetal development may impact kidney function in adult offspring. The involved pathways seem to be a nonspecific imprinting process rather than specific to kidney development or function.     

Cocaine-mediated downregulation of microglial miR-124 expression involves promoter DNA methylation

Neuroinflammation plays a critical role in the development of reward-related behavior in cocaine self-administration rodents. Cocaine, one of most commonly abused drugs, has been shown to activate microglia both in vitro and in vivo. Detailed molecular mechanisms underlying cocaine-mediated microglial activation remain poorly understood. microRNAs (miRs) belonging to a class of small noncoding RNA superfamily have been shown to modulate the activation status of microglia. miR-124, one of the microglia-enriched miRs, functions as an anti-inflammatory regulator that maintains microglia in a quiescent state. To date, the possible effects of cocaine on microglial miR-124 levels and the associated underlying mechanisms have not been explored. In the current study, we demonstrated that cocaine exposure decreased miR-124 levels in both BV-2 cells and rat primary microglia. These findings were further validated in vivo, wherein we demonstrated decreased abundance of miR-124 in purified microglia isolated from cocaine-administered mice brains compared with cells from saline administered animals. Molecular mechanisms underlying these effects involved cocaine-mediated increased mRNA and protein expression of DNMTs in microglia. Consistently, cocaine substantially increased promoter DNA methylation levels of miR-124 precursors (pri-miR-124-1 and ?2), but not that of pri-miR-124-3, both in vitro and in vivo. In summary, our findings demonstrated that cocaine exposure increased DNA methylation of miR-124 promoter resulting into its downregulation, which, in turn, led to microglial activation. Our results thus implicate that epigenetic modulation of miR-124 could be considered as a potential therapeutic approach to ameliorate microglial activation and, possibly, the development of cocaine addiction.     

Epigenetic effects of prenatal stress on 11β-hydroxysteroid dehydrogenase-2 in the placenta and fetal brain

Maternal exposure to stress during pregnancy is associated with significant alterations in offspring neurodevelopment and elevated maternal glucocorticoids likely play a central role in mediating these effects. Placental 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2) buffers the impact of maternal glucocorticoid exposure by converting cortisol/corticosterone into inactive metabolites. However, previous studies indicate that maternal adversity during the prenatal period can lead to a down-regulation of this enzyme. In the current study, we examined the impact of prenatal stress (chronic restraint stress during gestational days 14-20) in Long Evans rats on HSD11B2 mRNA in the placenta and fetal brain (E20) and assessed the role of epigenetic mechanisms in these stress-induced effects. In the placenta, prenatal stress was associated with a significant decrease in HSD11B2 mRNA, increased mRNA levels of the DNA methyltransferase DNMT3a, and increased DNA methylation at specific CpG sites within the HSD11B2 gene promoter. Within the fetal hypothalamus, though we find no stress-induced effects on HSD11B2 mRNA levels, prenatal stress induced decreased CpG methylation within the HSD11B2 promoter and increased methylation at sites within exon 1. Within the fetal cortex, HSD11B2 mRNA and DNA methylation levels were not altered by prenatal stress, though we did find stress-induced elevations in DNMT1 mRNA in this brain region. Within individuals, we identified CpG sites within the HSD11B2 gene promoter and exon 1 at which DNA methylation levels were highly correlated between the placenta and fetal cortex. Overall, our findings implicate DNA methylation as a mechanism by which prenatal stress alters HSD11B2 gene expression. These findings highlight the tissue specificity of epigenetic effects, but also raise the intriguing possibility of using the epigenetic status of placenta to predict corresponding changes in the brain.     

Gestational stress induces depressive-like and anxiety-like phenotypes through epigenetic regulation of BDNF expression in offspring hippocampus

Exposure to stressful life events during pregnancy exerts profound effects on neurodevelopment and increases the risk for several neurodevelopmental disorders including major depression. The mechanisms underlying the consequences of gestational stress are complex and remain to be elucidated. This study investigated the effects of gestational stress on depressive-like behavior and epigenetic modifications in young adult offspring. Gestational stress was induced by a combination of restraint and 24-hour light disturbance to pregnant dams throughout gestation. Depressive-like and anxiety-like behaviors of young adult offspring were examined. The expression and promoter methylation of brain derived neurotrophic factor (BDNF) were measured using RT-qPCR, Western blot, methylated DNA immunoprecipitation (MeDIP) and chromatin immunoprecipitation (ChIP). In addition, the expressions of histone deacetylases (HDACs) and acetylated histone H3 lysine 14 (AcH3K14) were also analyzed. Our results show that offspring from gestational stress dams exhibited depressive-like and anxiety-like behaviors. Biochemically, stress-offspring showed decreased expression of BDNF, increased expression of DNMT1, HDAC1, and HDAC2, and decreased expression of AcH3K14 in the hippocampus as compared to non-stress offspring. Data from MeDIP and ChIP assays revealed an increased methylation as well as decreased binding of AcH3K14 on specific BDNF promoters. Pearson analyses indicated that epigenetic changes induced by gestational stress were correlated with depressive-like and anxiety-like behaviors. These data suggest that gestational stress may be a suitable model for understanding the behavioral and molecular epigenetic changes observed in patients with depression.     

Early Maternal Alcohol Consumption Alters Hippocampal DNA Methylation,Gene Expression and Volume in a Mouse Model

The adverse effects of alcohol consumption during pregnancy are known, but the molecular events that lead to the phenotypic characteristics are unclear. To unravel the molecular mechanisms, we have used a mouse model of gestational ethanol exposure, which is based on maternal ad libitum ingestion of 10% (v/v) ethanol for the first 8 days of gestation (GD 0.5-8.5). Early neurulation takes place by the end of this period, which is equivalent to the developmental stage early in the fourth week post-fertilization in human. During this exposure period, dynamic epigenetic reprogramming takes place and the embryo is vulnerable to the effects of environmental factors. Thus, we hypothesize that early ethanol exposure disrupts the epigenetic reprogramming of the embryo, which leads to alterations in gene regulation and life-long changes in brain structure and function. Genome-wide analysis of gene expression in the mouse hippocampus revealed altered expression of 23 genes and three miRNAs in ethanol-exposed, adolescent offspring at postnatal day (P) 28. We confirmed this result by using two other tissues, where three candidate genes are known to express actively. Interestingly, we found a similar trend of upregulated gene expression in bone marrow and main olfactory epithelium. In addition, we observed altered DNA methylation in the CpG islands upstream of the candidate genes in the hippocampus. Our MRI study revealed asymmetry of brain structures in ethanol-exposed adult offspring (P60): we detected ethanol-induced enlargement of the left hippocampus and decreased volume of the left olfactory bulb. Our study indicates that ethanol exposure in early gestation can cause changes in DNA methylation, gene expression, and brain structure of offspring. Furthermore, the results support our hypothesis of early epigenetic origin of alcohol-induced disorders: changes in gene regulation may have already taken place in embryonic stem cells and therefore can be seen in different tissue types later in life.